Oxidation behaviour of a PVD processed Mg-14Ti alloy

Abstract

The oxidation behaviour in air of a physical vapour deposited (PVD) Mg-14Ti (wt. %) alloy was studied in the 325-450 °C temperature range. The 2-3 mm thick deposit was grown in two stages. The first half of the deposit was mechanically worked during the process and then, deposition went on without this flailing period. The microstructure of the deposit can be divided into two parts. each one involving half of the total thickness. The oxidation resistance is strongly affected by the microstructure of the deposit, flailed or unflailed. Unflailed part of the deposit presents open boundaries with a high density of defects. Internal oxidation can proceed through this kind of boundaries. This is the reason of anomalous behaviour during the initial stages of oxidation, with maximum mass gain at 350 °C. The flailed part shows a few cracks but the grain boundaries are practically free of defects. Flaws and cracks act as the starting point for the development of large intrusions, which contribute substantially to the total mass gain of the alloy, especially with increasing the temperature.